The present invention relates to moisture curable organopolysiloxanes having terminal 1,3-dicarbonyl cyclic alkoxyorganosiloxy units.
Prior to the present invention, one-package moisture curable organopolysiloxane compositions consisting essentially of chemically combined units of the formula, ##STR1## where R is a monovalent organic radical, generally had an organo silyl functional unit sensitive to atmospheric moisture, such as silylacyloxy unit, a silylketoximato unit, silylaminoxy unit, etc. These moisture sensitive organopolysiloxane compositions were generally maintained as a pigmented moisture-free reinforced mixture in a moisture resistant collapsible tube. Cure of the flowable organopolysiloxane was effected when the flowable mixture was applied onto a substrate under atmospheric conditions. In some instances it took several hours before the mixture attained a tack-free condition while in other situations the cure of the mixture was accompanied by an unpleasant amine odor or acid odor, such as acetic acid. In other situations, the moisture curable organopolysiloxane caused corrosion of metallic surfaces.
It would be desirable to overcome the aforementioned undesirable shortcomings of one-package room temperature vulcanizing organopolysiloxane compositions by providing a one-package organopolysiloxane composition capable of being converted from a flowable state to an elastomeric state upon exposure to atmospheric moisture to produce a tack-free elastomer within about one hour or less and cured organopolysiloxane elastomer within 24 hours without the generation of amine or acid by-products causing undesirable odor and metal contamination.
As shown in the copending application Ser. No. 927,289 of James A. Cella, filed concurrently herewith and assigned to the same assignee as the present invention, moisture curable compositions having terminal 1,3-dicarbonyl cyclic organosiloxy units of the formula, ##STR2## where R, R.sup.1, X, Y and Z are defined below and d is equal to 0 or 1, have been found to be convertible to valuable organopolysiloxane elastomers without forming corrosive or foul smelling by-products. However, the usable work life of the moisture curable organopolysiloxane is often insufficient to utilize such curable organopolysiloxanes in a variety of applications.